Before answering this question let us understand how setting up a wrong profile picture might end up with your number getting banned.
There are a lot of spammers and there are chances you also might have come across one of them irritating you by sending bulk WhatsApp messages intimidating you to buy those 3 shirts for Rs 999 or sending you a ton of random new mobile numbers that you can buy.
Think of a scenario, someone sends this message to you on WhatsApp

There is no profile picture and you can’t even see the name of the sender.
And since this message is promotional, there is a high chance you will block and report them thinking the sender is a spammer.
And if the spammer gets reported by too many people, then WhatsApp will ban their number from their platform.

Now, coming back to the original question, what profile picture should you use to reduce the chances of number banning?
Well if you don’t want to come across as a spammer, the least you can do is have a profile picture and name that is easy to recognize and makes you come across as genuine.
Also, make sure that your privacy settings are appropriately set so that the user can see your profile picture and name even if he does not have your number saved or you don’t add his number.
i.e. set the About and Profile photo option in the privacy settings to ‘Everyone’.

BONUS CLIP: You can also use this Pro feature which can help to reduce the number-banning chances.
There is no guarantee that the number will not be blocked if you do this but it reduces the chance of number blocking.